Method and system for PHY loop detection

ABSTRACT

A method, system and apparatus are provided for detecting a loop-back in a physical layer on an Ethernet link. In the physical layer, a device sends a base page on the Ethernet link. The base page has at least one next page capability bit set. Subsequently, the device receives a received base page. Thereafter, for detecting the loop-back, the next page capability bit is set in the received base page is determined.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of the following application, U.S.patent application Ser. No. 11/287,047, entitled Method and System forLoop Detection, filed on Nov. 25, 2005, which is hereby incorporated byreference, as if it is set forth in full in this specification.

BACKGROUND OF THE INVENTION

1. Field of Invention

Embodiments of the invention relate in general to communication inEthernet. More specifically, the embodiments of the invention relate toa method and a system for the detection of a loop in the physical layerof an Ethernet port.

2. Description of the Background Art

A seven-layer architecture, known as Open System Interconnect (OSI)model, is commonly used for communication in computer networks. TheEthernet is a Local Area Network (LAN) technology that defines wiringand signaling of the physical layer of the OSI model. The Ethernet alsodefines protocols for Media Access Control (MAC) or the data link layerof the OSI model, and the format for transmitting frames. The physicallayer is also known as PHY or layer 1 and the data link layer is knownas layer 2.

In the case of a fault, an incorrect configuration or a non-compliantinstallation, a data packet sent from a computer that is connected to anetwork may not reach the PHY of a destination computer. Further, thesent data packet may incorrectly revert to the sending computer. Such asituation is referred to as a “loop-back.” The reverting of data packetsmay overload the CPU of the sending computer, and also result in theloss of data. Further, the reverting may cause problems in the normaloperation of other applications executing on the sending computer.

An existing method for detection of loop-back faults is known as a‘keep-alive mechanism’. The keep-alive mechanism transmits and receivesspecial data. If the sending computer receives the transmitted specialpacket, a loop-back link fault is declared and transmission of data isstopped. However, the keep-alive mechanism requires layer 2 to transmitframes. Once layer 2 is in communication, other applications on acomputer may also use it for transmitting and receiving data. Aloop-back may cause problems in the functioning of the otherapplications. Moreover, the keep-alive mechanism requires a CPU toconstantly generate frames to detect a loop-back, which results in theconsumption of CPU resources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary environment wherein the embodiments ofthe invention can be practiced.

FIG. 2 is a block diagram of a system for detecting loop-back, inaccordance with an exemplary embodiment of the present invention.

FIG. 3 is a flowchart depicting a method for detecting loop-back, inaccordance with an exemplary embodiment of the present invention.

FIG. 4 is a flowchart depicting a method for detecting loop-back, inaccordance with another exemplary embodiment of the present invention.

FIG. 5 is a flowchart depicting a method for detecting loop-back, inaccordance with yet another exemplary embodiment of the invention.

FIG. 6 is a flowchart depicting a method for performing auto negotiationand detecting loop-back, in accordance with still another exemplaryembodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The various embodiments of the invention provide a method, a system, anda computer-readable medium for detecting loop-back in a physical layeron an Ethernet link. The Ethernet link uses a process known as ‘autonegotiation’ to determine the capabilities of the PHY devices at eitherend of the Ethernet link. The PHY device in auto negotiation processsends data formatted as a “base page” and a “next page”. The base pagecontains basic information necessary for operation of the Ethernet linkand the next page contains information that may not be necessary for theoperation of the link. The base page includes information regarding thetype of Ethernet connection supported, next page capability and soforth. The next page includes a message page, format of message page andso forth. In an embodiment of the invention, a device sends a base page,followed by zero or more sent next pages on the physical layer of theEthernet link. The device also receives a base page, followed by zero ormore next pages. Thereafter, a loop-back is declared, if the sent nextpages and the received next pages match.

FIG. 1 illustrates an exemplary environment 100 wherein the embodimentof the invention can be practiced. Environment 100 can contain a networklink. According to the various embodiments of the invention, the networklink can be an Ethernet link 102. Ethernet link 102 includes a firstdevice 104 and a second device 106, in accordance with an exemplaryembodiment of the present invention. In various embodiments of theinvention, first device 104 and second device 106 can be a Data TerminalEquipment (DTE) or a processing device, for example, a personalcomputer, a general-purpose computer, a laptop, a palmtop, etc. In anembodiment of the invention, second device 106 is a link partner tofirst device 104.

In an embodiment of the invention, first device 104 communicates withsecond device 106 over Ethernet link 102. Ethernet link 102 can includenetworks such as Local Area Network (LAN), Wide Area Network (WAN),Metropolitan Area Network (MAN), Personal Area Network (PAN), IndustrialEthernet network, home network, and so forth.

First device 104 establishes a link with second device 106 to startcommunication. The link is established at the physical layer of firstdevice 104 and second device 106. The physical layer is defined in aseven-layer architecture model, known as the Open System Interconnect(OSI) model. The OSI model is used for communication in computernetworks. The physical layer is also known as PHY or layer 1.

In an embodiment of the invention, an auto-negotiation feature,described by Institute of Electrical & Electronic Engineers (IEEE) etal., i.e., IEEE 802.3-2004 Clause 28, is used to establish the link.Auto-negotiation uses a series of link pulses known as a Fast LinkPulses (FLP) burst to encode a 16-bit word. The FLP burst interweaves aclock pulse with a data pulse to encode a 16-bit word, known as a linkcode word. The link code word may be in the format known as a base pageor may be an optional extension format known as a next page. In anembodiment of the invention, first device 104 exchanges base pages withsecond device 106, to establish the link. After the link is established,data transmission may be started by connecting the data link layer offirst device 104 to the data link layer of second device 106. The datalink layer is defined in the OSI model and is also known as layer 2.

In an embodiment of the invention, second device 106 can have functionsthat are identical to that of first device 104.

FIG. 2 is a block diagram of a system 200 for detecting loop-back, inaccordance with an exemplary embodiment of the present invention. System200 includes a next page capability checker 202, a next page sender 204,a next page receiver 206, and a next page comparer 208. In an embodimentof the invention, the elements of system 200 are located on first device104. In another embodiment of the invention, the elements of system 200are also located on second device 106.

In an embodiment of the invention, a base page includes the informationpertaining to the capabilities of a device. The capabilities of thedevice include the mode of the Ethernet connection supported, such as 10Base-T, 10 Base-T Full Duplex, 100 Base-TX, 100 Base-TX Full Duplex, 100Base-T4, and so forth. The capabilities also include other parameterssuch as the capability of a device to send and receive a next page. Thenext page is a medium for transmitting additional information beyond theinformation transmitted by the base pages. The additional informationtransmitted by the next page includes proprietary information relatingto the device. Next page capability checker 202 checks the capability ofsecond device 106 to send and receive next pages. In an embodiment ofthe invention, next page capability checker 202 sends and receives basepages to check the capability of second device 106 to send and receivenext pages. In another embodiment of the invention, next page capabilitychecker 202 compares the sent and received base pages to check thecapability of second device 106 to send and receive next pages. In anembodiment of the invention, next page capability checker 202 declares aloop-back or a no loop-back condition based on the result of comparisonof the sent and received base pages.

In an embodiment of the invention, next page capability checker 202reads and updates an Auto-Negotiation Advertisement Register (ANAR) andan Auto-Negotiation Link Partner Advertisement Register (ANLPAR). TheANAR and ANLPAR registers are defined for the PHY of first device 104.The ANAR is used to set the capabilities of first device 104. Theinformation in ANAR is sent in a sent base page. The ANLPAR includesinformation on the capabilities of second device 106. The ANLPAR isupdated on the receipt of a received base page from second device 106.If the ANLPAR indicates that the second device is not capable of nextpage then next page capability checker 202 declares a no loop-backcondition.

Next page sender 204 sends a sent next page from first device 104 tosecond device 106. In an embodiment of the invention, next page sender204 sends the sent next page, based on the capability of second device106 to send and receive next pages. In an embodiment of the invention,next page sender 204 reads an Auto-Negotiation Expansion Register (ANER)and an Auto-Negotiation Next Page Transmit Register (ANNPTR). In anotherembodiment of the invention, next page sender 204 updates the ANNPTR.The ANER and the ANNPTR are defined for the PHY of first device 104. TheANER includes information such as the next page capability of firstdevice 104, the next page capability of second device 106, theauto-negotiation capability of second device 106, the receipt of a newpage, a parallel detection fault, and so forth. The ANNPTR is used toset the information that is to be sent in the sent next page from firstdevice 104. In another embodiment of the invention, next page sender 204may send next pages with an NP bit set to 0.

Next page receiver 206 receives a received next page from second device106. The received next page is received at first device 104. In anembodiment of the invention, next page receiver 206 reads the ANER andan Auto-Negotiation Link Partner Next Page Receive Register (ANLPNPRR).The ANLPNPRR is defined for the PHY of first device 104. The ANLPNPRRincludes the information contained in the received next page. In anotherembodiment of the invention, next page receiver 206 may receive a nextpage from a far end device.

Next page comparer 208 compares the sent next page and the received nextpage. In an embodiment of the invention, next page comparer 208 readsand compares the information included in the ANNPTR and the ANLPNPRR. Inan embodiment of the invention, next page comparer 208 declaresloop-back, based on the results of the comparison. In another embodimentof the invention, next page comparer 208 also declares a no loop-backcondition.

In an embodiment of the invention, next page sender 204, next pagereceiver 206, and next page comparer 208 function sequentially to send,receive and compare next pages. In another embodiment of the invention,one or more of next page sender 204, next page receiver 206, and nextpage comparer 208 may not be required to function to detect loop-back.For example, next page sender 204, next page receiver 206, and next pagecomparer 208 are not required if the second device is not capable ofsending or receiving a next page.

In various embodiments of the invention, elements of system 200, such asnext page sender 204, next page receiver 206, and next page comparer208, is implemented in the form of software, hardware, firmware, ortheir combination thereof.

FIG. 3 is a flowchart depicting a method for detecting a loop-back, inaccordance with an exemplary embodiment of the present invention. Atstep 302, a base page is sent from a device in the physical layer. In anembodiment of the invention, the base page is sent on an Ethernet link.The base page has next page capability bit set. Thereafter, at step 304,a base page is received by the device. In an embodiment, the receivedbase page can be a base page transmitted by second device 106. At step306, the next page capability bit is determined in the received basepage to detect the loop-back in the physical layer. In an embodiment ofthe invention, the next page capability bit is examined in the receivedbase page to detect the loop-back in the physical layer. In anembodiment of the invention, if the next page capability bit is not setin the received base page, then it is decided that no loop-back exists.In another embodiment of the invention, if the next page capability isset in the received base page, then next pages are sent to detect theloop-back. In an embodiment of the invention, the next pages are sent byfirst device 104.

FIG. 4 is a flowchart depicting a method for detecting loop-back, inaccordance with another exemplary embodiment of the present invention.At step 402, a sent base page is sent from a first device in thephysical layer. The sent base page is followed by zero or more sent nextpages. Subsequently, at step 404, a received base page is received atthe first device. The received base page is followed by zero or morereceived next pages. In an embodiment of the invention, a second devicesends the received next page. In an embodiment of the invention, if thesecond device does not send the received next page, then a no loop-backcondition is declared. At step 406, the sent next page is compared tothe received next page. In an embodiment of the invention, zero or moresent next pages and received next pages are compared. At step 408,loop-back is declared if the sent next page matches the received nextpage. In an embodiment of the invention, loop-back is declared if thezero or more sent next pages match the zero or more received next pages.This is explained in detail in conjunction with FIG. 5.

FIGS. 5 a and 5 b is a flowchart depicting a method for detectingloop-back, in accordance with yet another exemplary embodiment of theinvention. At step 502, a first device sends a sent base page to asecond device. At step 504, the first device receives a received basepage. In an embodiment of the invention, the second device sends thereceived base page. In various embodiments of the invention, next pagecapability checker 202 is utilized to send the sent base page and toreceive the received base page. In an embodiment of the invention, theANER is checked for a ‘page received’ bit. The page received bit, if setto ‘1’ in the ANER, indicates the receipt of the received base page. Inan embodiment of the invention, the received base page is similar to thesent base page.

At step 506, the sent base page is compared to the received base page.In various embodiments of the invention, the comparison is achieved byutilizing next page capability checker 202. In an embodiment of theinvention, the sent base page is compared to the received base page bychecking a Next Page (NP) bit in the ANLPAR and the ANAR. In anembodiment of the invention, the NP bit is set to ‘1’ in the ANAR. In anembodiment of the invention, if the NP bit is set to ‘0’ in the ANLPAR,then there is no loop-back. In another embodiment of the invention, ifthe NP bit is set to ‘0’ in the ANLPAR, then the second device is notcapable of sending and receiving next pages. Subsequently, a noloop-back condition is declared at step 514. In various embodiments ofthe invention, the no loop-back condition is declared by utilizing nextpage capability checker 202.

In an embodiment of the invention, if the NP bit is also set to ‘1’ inthe ANLPAR, then the second device is capable of sending and receiving anext page. In another embodiment of the invention, if the NP bit is alsoset to ‘1’ in the ANLPAR, then there may be a loop-back. In anotherembodiment of the invention, the sent base page is reverted to the firstdevice as a received base page.

In an embodiment of the invention, if the information in ANAR matchesthe information in ANLPAR, then there may be a loop-back. In anotherembodiment of the invention, if the information in ANAR matches theinformation in ANLPAR, then the second device may be a valid PHY, whichis capable of sending and receiving next pages.

Further, more information is required if the information in ANAR matchesthe information in ANLPAR. In an embodiment of the invention, moreinformation is acquired by exchanging next pages between the firstdevice and the second device. The information exchanged by next pagesincludes the formatting of the next page, a message code, etc. Forexample, the next page may be formatted as a message page or anunformatted page.

At step 508, the first device sends a sent next page to the seconddevice. In various embodiments of the invention, the sent next page issent by utilizing next page sender 204. In an embodiment of theinvention, the sent next page is an unformatted page. An unformattedpage is 11-bit long. In an embodiment of the invention, the sent nextpage contains the Media Access Control (MAC) address of the firstdevice. The MAC address is the hard-coded address of the PHY of thefirst device, and is a globally unique address for each networkinterface controller. The MAC address is 48-bit long. In a preferredembodiment of the invention, the first device sends five sent nextpages. The five sent next pages are required to specify the MAC addressof the first device.

In an embodiment of the invention, the next pages are sent one afteranother. The information in each next page is updated in the ANNPTR. Inan embodiment of the invention, the page received bit of the ANER ischecked to verify the receipt of the received next page.

At step 510, a received next page is received at the first device. Thereceived next page can be sent by the second device to the first device.In various embodiments of the invention, the received next page isreceived by utilizing next page receiver 206. In an embodiment of theinvention, the received next page contains the MAC address of the seconddevice. In an embodiment of the invention, five received next pages arereceived at the first device.

At step 512, the sent next page is compared to the received next page.In various embodiments of the invention, the comparison is achieved byutilizing next page comparer 208. In an embodiment of the invention, theinformation pertaining to the ANNPTR is compared to the information inthe ANLPNPRR. In another embodiment of the invention, the MAC addresssent in the sent next page is compared to the MAC address received inthe received next page. In yet another embodiment of the invention, an‘acknowledge’ bit in the ANLPNPRR is checked. The acknowledge bit, if itis set to ‘1’ in the ANLPNPRR, indicates that the sent next page hasbeen received by a valid PHY.

At step 514, no loop-back condition is declared. In various embodimentsof the invention, the no loop-back condition is declared by utilizingnext page comparer 208. In an embodiment of the invention, no loop-backcondition is declared if the acknowledge bit is set to ‘1’ in theANLPNPRR. In another embodiment of the invention, no loop-back conditionis declared if the information in the ANNPTR does not match theinformation in ANLPNRR.

In an embodiment of the invention, if the sent next page and thereceived next page do not match, then a further next page is sent withthe NP bit set to ‘0’, to terminate the transmission.

In an embodiment of the invention, a series of next page transfers andcomparisons are made to establish a loop-back or no loop-back condition.

At step 516, loop-back is declared if the information in ANNPTR matchesthe information in ANLPNPRR. In various embodiments of the invention,the loop-back is declared by utilizing next page comparer 208. In anembodiment of the invention, loop-back is declared if the acknowledgebit is set to ‘0’ in the ANLPNPRR.

In an embodiment of the invention, if the first device is not capable ofsending next pages and next page capability checker 202 detects that thesecond device is also not capable of sending next pages, a no loop-backcondition is declared and the first device may use base pages to changethe PHY link parameters.

In an embodiment of the invention, the PHY does not set the link up, inthe event of a loop-back. The link up is required for data transmissionfrom layer 2.

In an embodiment of the invention, for the first device that do notsupport an ‘ack2’ function, an ‘ack2’ bit is set to ‘0’ in the nextpages transmitted to the second device, as any other message codes arenot supported by such devices.

FIGS. 6 a and 6 b is a flowchart depicting a method for performing autonegotiation and detecting loop-back, in accordance with still anotherexemplary embodiment of the invention. At step 602, an auto negotiationfeature of the physical layer of first device 104 is enabled. In anembodiment of the invention, the auto negotiation feature is requiredfor automatic configuration of the physical layers. At step 604, aconfiguration option ‘down-when-looped’ of the physical layer ischecked. Thereafter, at step 606, if the ‘down-when-looped’configuration option is not enabled then the auto negotiation is carriedout in the hardware. In an embodiment of the invention, if the‘down-when-looped’ configuration option is not enabled then the methodprovided by the invention is not used for detecting the loop-back. Atstep 608, if the down when looped option is enabled, then first device104 is enabled to send next pages. Subsequently, a sent base page issent from first device 104. Thereafter, a received base page is receivedat first device 104. In an embodiment of the invention, the receivedbase page is sent by second device 106. At step 610, the autonegotiation capability of second device 106 is checked. In an embodimentof the invention, the auto negotiation capability of second device 106is checked by transmitting base pages. At step 612, if the autonegotiation feature of second device 106 is not enabled then a paralleldetection is carried out in the hardware. At step 612, if the autonegotiation feature of the second device 106 is enabled, then autonegotiation is carried out, at step 614. At step 614, the capability ofsecond device 106 to automatically send next pages is checked. In anembodiment of the invention, the capability of second device 106 to sendnext pages is checked by using next page capability checker 202. At step616, if second device 106 is not able to automatically send next pagesthen auto negotiation is carried out in hardware. At step 618, a sentnext page is sent from first device 104, if second device 106 is able toautomatically send next pages. In an embodiment of the invention, nextpage sender 204 is used to send the sent next page. At step 620, areceived next page is received at first device 104. In an embodiment ofthe invention, the received next page is sent by second device 106. Inan embodiment of the invention, next page receiver 206 is used toreceive the received next page. At step 622, if the received next pagehas a next page message code, then a no loop-back is declared.Thereafter, the ack bit in ANLPNPRR is set to ‘0’ and transmission ofnext pages is stopped, at step 624. At step 622, if the received nextpage does not have a next page message code, then the sent next page andthe received next page are compared, at step 626. In an embodiment ofthe invention, the sent next page and the received next page arecompared by next page comparer 208. At step 626, if the sent next pageis not identical to the received next pages then a no loop-back isdeclared. At step 628, a no loop-back is declared and a last sent nextpage is sent and auto negotiation is stopped. At step 630, if the sentnext page and the received next page are identical, then more sent nextpages are sent. At step 630, if all the sent next pages and the receivednext pages are identical then a loop-back is declared andauto-negotiation is completed.

A DTE power detect mechanism in a PHY may use a principle that isanalogous to the methods provided by the embodiments of the invention.The DTE detect mechanism provided in a patent publication US20040186689,assigned to Cisco Technology Inc. is incorporated as a reference herein.However, both cannot be supported simultaneously. Moreover, a PHY suchas Intel™ LXT9785 does not allow next page capability if the DTE powerdetect mechanism is enabled. In an embodiment of the invention, the DTEpower detect mechanism may use the methods provided by the variousembodiments of the invention, if the port is connected to a powereddevice or a PHY. In another embodiment of the invention, the DTE powerdetect may be made mutually exclusive to a ‘down-when-looped’ feature.In an embodiment of the invention, the ‘down-when-looped’ featureindicates that the link is down when loop-back is detected. In anembodiment of the invention, the ‘down-when-looped’ feature is turnedoff by default.

In an embodiment of the invention, if the platforms use the next pagewith the standard message code, then the methods provided by the variousembodiments of the invention may be added to the messages that areexchanged.

Embodiments of the present invention provide a method and a system todetect a PHY loop-back. The loop-back is detected before linking up thelayer 2, which prevents data loss. The embodiments of the invention alsoresult in a reduction in the consumption of resources of the CPU of adevice. The consumption of resources is reduced, as the CPU is notrequired to constantly send and receive frames to detect loop-back.

Although the invention has been discussed with respect to specificembodiments thereof, these embodiments are merely illustrative, and notrestrictive, of the invention. For example, a ‘method for detecting aPHY loop-back’ can include any type of analysis, manual or automatic, toanticipate the needs of detecting a loop-back.

Although specific protocols have been used to describe embodiments,other embodiments can use other transmission protocols or standards. Useof the terms ‘peer’, ‘client’, and ‘server’ can include any type ofdevice, operation, or other process. The present invention can operatebetween any two processes or entities including users, devices,functional systems, or combinations of hardware and software.Peer-to-peer networks and any other networks or systems where the rolesof client and server are switched, change dynamically, or are not evenpresent, are within the scope of the invention.

Any suitable programming language can be used to implement the routinesof the present invention including C, C++, Java, assembly language, etc.Different programming techniques such as procedural or object orientedcan be employed. The routines can execute on a single processing deviceor multiple processors. Although the steps, operations, or computationsmay be presented in a specific order, this order may be changed indifferent embodiments. In some embodiments, multiple steps shownsequentially in this specification can be performed at the same time.The sequence of operations described herein can be interrupted,suspended, or otherwise controlled by another process, such as anoperating system, kernel, etc. The routines can operate in an operatingsystem environment or as stand-alone routines occupying all, or asubstantial part, of the system processing.

In the description herein for embodiments of the present invention,numerous specific details are provided, such as examples of componentsand/or methods, to provide a thorough understanding of embodiments ofthe present invention. One skilled in the relevant art will recognize,however, that an embodiment of the invention can be practiced withoutone or more of the specific details, or with other apparatus, systems,assemblies, methods, components, materials, parts, and/or the like. Inother instances, well-known structures, materials, or operations are notspecifically shown or described in detail to avoid obscuring aspects ofembodiments of the present invention.

Also in the description herein for embodiments of the present invention,a portion of the disclosure recited in the specification containsmaterial, which is subject to copyright protection. Computer programsource code, object code, instructions, text or other functionalinformation that is executable by a machine may be included in anappendix, tables, figures or in other forms. The copyright owner has noobjection to the facsimile reproduction of the specification as filed inthe Patent and Trademark Office. Otherwise all copyright rights arereserved.

A ‘computer’ for purposes of embodiments of the present invention mayinclude any processor-containing device, such as a mainframe computer,personal computer, laptop, notebook, microcomputer, server, personaldata manager or ‘PIM’ (also referred to as a personal informationmanager), smart cellular or other phone, so-called smart card, set-topbox, or any of the like. A ‘computer program’ may include any suitablelocally or remotely executable program or sequence of codedinstructions, which are to be inserted into a computer, well known tothose skilled in the art. Stated more specifically, a computer programincludes an organized list of instructions that, when executed, causesthe computer to behave in a predetermined manner. A computer programcontains a list of ingredients (called variables) and a list ofdirections (called statements) that tell the computer what to do withthe variables. The variables may represent numeric data, text, audio orgraphical images. If a computer is employed for presenting media via asuitable directly or indirectly coupled input/output (I/O) device, thecomputer would have suitable instructions for allowing a user to inputor output (e.g., present) program code and/or data informationrespectively in accordance with the embodiments of the presentinvention.

A ‘computer readable medium’ for purposes of embodiments of the presentinvention may be any medium that can contain, store, communicate,propagate, or transport the computer program for use by or in connectionwith the instruction execution system apparatus, system or device. Thecomputer readable medium can be, by way of example only but not bylimitation, an electronic, magnetic, optical, electromagnetic, infrared,or semiconductor system, apparatus, system, device, propagation medium,or computer memory.

Reference throughout this specification to “one embodiment”, “anembodiment”, or “a specific embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention and notnecessarily in all embodiments. Thus, respective appearances of thephrases “in one embodiment”, “in an embodiment”, or “in a specificembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics of any specificembodiment of the present invention may be combined in any suitablemanner with one or more other embodiments. It is to be understood thatother variations and modifications of the embodiments of the presentinvention described and illustrated herein are possible in light of theteachings herein and are to be considered as part of the spirit andscope of the present invention.

Further, at least some of the components of an embodiment of theinvention may be implemented by using a programmed general-purposedigital computer, by using application specific integrated circuits,programmable logic devices, or field programmable gate arrays, or byusing a network of interconnected components and circuits. Connectionsmay be wired, wireless, by modem, and the like.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application.

Additionally, any arrows in the drawings/Figures should be consideredonly as exemplary, and not limiting, unless otherwise specificallynoted. Combinations of components or steps will also be considered asbeing noted, where terminology is foreseen as rendering the ability toseparate or combine is unclear.

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the abstract, is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed herein. While specific embodiments of, and examples for, theinvention are described herein for illustrative purposes only, variousequivalent modifications are possible within the spirit and scope of thepresent invention, as those skilled in the relevant art will recognizeand appreciate. As indicated, these modifications may be made to thepresent invention in light of the foregoing description of illustratedembodiments of the present invention and are to be included within thespirit and scope of the present invention.

Thus, while the present invention has been described herein withreference to particular embodiments thereof, a latitude of modification,various changes and substitutions are intended in the foregoingdisclosures, and it will be appreciated that in some instances somefeatures of embodiments of the invention will be employed without acorresponding use of other features without departing from the scope andspirit of the invention as set forth. Therefore, many modifications maybe made to adapt a particular situation or material to the essentialscope and spirit of the present invention. It is intended that theinvention not be limited to the particular terms used in followingclaims and/or to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include any and all embodiments and equivalents falling within thescope of the appended claims.

1. A method comprising: sending in a physical layer, by a device on anethernet link, a base page with an indicator that indicates that aloop-back in the physical layer exists; receiving in the physical layer,by the device on the ethernet link, a received base page; and examiningthe indicator in the received base page for detecting a loop-back in thephysical layer.
 2. The method of claim 1, wherein examining theindicator comprises at least one of: deciding to continue with theloop-back detection if the indicator is set in the received base page;and deciding that the loop-back does not exist if the indicator is notset in the received base page.
 3. The method of claim 2, whereindeciding to continue with the loop-back detection comprises deciding tocommence sending at least one next page, if the indicator is set in thereceived base page.
 4. The method of claim 3, wherein the at least onesent next page comprises five sent next pages, and wherein at least onereceived next page comprises five received next pages.
 5. The method ofclaim 4, the method further comprises: comparing respectively the fivesent next pages with the five received next pages; and declaring aloop-back if the five sent next pages respectively match the fivereceived next pages.
 6. The method of claim 4, wherein sending the atleast one next page comprises: checking a next page indicator in an autonegotiation link partner advertisement register (ANLPAR); and sendingthe sent next pages, if the next page indicator is set in the ANLPAR. 7.The method of claim 6, wherein sending the sent next pages comprisesencoding a media access control (MAC) address of the device in the sentnext pages.
 8. The method of claim 4, wherein receiving the at least onereceived next pages comprises: checking an auto negotiation expansionregister (ANER) for a next-page received bit; and reading anauto-negotiation link partner next page receive register (ANLPNPRR), ifthe next-page received bit is set in the ANER.
 9. A system comprising:means for sending in a physical layer a base page with an indicator thatindicates that a loop-back in the physical layer exists; means forreceiving in the physical layer a received base page; and means forexamining the indicator in the received base page for detecting aloop-back in the physical layer.
 10. The system of claim 9, whereinmeans for examining the indicator comprises at least one of: means fordeciding to continue with the loop-back detection if the indicator isset in the received base page; and means for deciding that the loop-backdoes not exist if the indicator is not set in the received base page.11. The system of claim 10, wherein means for deciding to continue withthe loop-back detection comprises deciding to commence sending at leastone next page, if the indicator is set in the received base page. 12.The system of claim 11, wherein the at least one sent next pagecomprises five sent next pages, and wherein at least one received nextpage comprises five received next pages.
 13. The system of claim 12, thesystem further comprises: means for comparing respectively the five sentnext pages with the five received next pages; and means for declaring aloop-back if the five sent next pages respectively match the fivereceived next pages.
 14. The system of claim 12, wherein means forsending the at least one next page comprises: means for checking a nextpage indicator in an auto negotiation link partner advertisementregister (ANLPAR); and means for sending the sent next pages, if thenext page indicator is set in the ANLPAR.
 15. The system of claim 14,wherein means for sending the sent next pages comprises encoding a mediaaccess control (MAC) address of a device in the sent next pages.
 16. Thesystem of claim 12, wherein means for receiving the at least onereceived next pages comprises: means for checking an auto negotiationexpansion register (ANER) for a next page received bit; and means forreading an auto-negotiation link partner next page receive register(ANLPNPRR), if the next-page received bit is set in the ANER.
 17. Amachine-readable non-transitory medium for detecting loop-back in aphysical layer on an Ethernet link including instructions executable bythe machine-readable non-transitory medium comprising: one or moreinstructions for sending in a physical layer a base page with anindicator that indicates that a loop-back in the physical layer exists;one or more instructions for receiving in the physical layer a receivedbase page; and one or more instructions for examining the indicator inthe received base page for detecting a loop-back in the physical layer.